2022.02.15 - 240. Lucky number in matrix

1. subject

2. Ideas

(1) Simulation

• ergodic matrix , Find out the minimum value of each row first , Find out the maximum value of each column , If there are duplicate elements , Indicates that the element is a lucky number .

3. Code

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class Test {
    
    public static void main(String[] args) {
    
    }
}

class Solution {
    
    public List<Integer> luckyNumbers(int[][] matrix) {
    
        int m = matrix.length;
        int n = matrix[0].length;
        List<Integer> res = new ArrayList<>();
        Set<Integer> set = new HashSet<>();
        for (int i = 0; i < m; i++) {
    
            int min = Integer.MAX_VALUE;
            for (int j = 0; j < n; j++) {
    
                min = Math.min(min, matrix[i][j]);
            }
            set.add(min);
        }
        for (int i = 0; i < n; i++) {
    
            int max = Integer.MIN_VALUE;
            for (int j = 0; j < m; j++) {
    
                max = Math.max(max, matrix[j][i]);
            }
            if (!set.add(max)) {
    
                res.add(max);
            }
        }
        return res;
    }
}